1. Field Of The Invention
This patent relates to fire resistant composite intermediate bulk containers. More particularly, this patent relates to a composite intermediate bulk container having a metal cage that has been made fire resistant by coating the surrounding metal cage with an intumescent paint or other intumescent coating.
2. Description Of The Related Art
Intermediate bulk containers (IBCs) are large industrial containers having a capacity of between 450 and 3,000 liters as defined in the Department of Transportation Hazardous Materials Regulations (between about 119 and 793 gallons), used to transport and store bulk liquids. IBCs may be made from heavy duty plastics, such as high molecular weight high density polyethylene, and can be formed into numerous shapes, including stackable cubes. A single 330 gallon IBC can replace six conventional 55 gallon drums, resulting in lower filling, dispensing, handling and storage and disposal costs.
One particular type of IBC, composite IBCs, may include in their design a metal cage, usually made of steel, that surrounds the plastic container to provide support and protection and to facilitate stacking of the composite IBCs. Composite IBCs typically include a pallet for extra strength and to allow transporting the composite IBC by forklift truck. Composite IBCs typically have a fillport located on top for filling and mixing of liquids, and a discharge valve at or near the bottom to facilitate dispensing of the contents. The inner plastic container, or bottle, may be replaced as needed, in reconditioning and reuse of the IBC.
Despite their reputation for lower cost, reliability and recyclability, composite IBCs have not been widely used for transporting flammable and combustible liquids because they have not yet been approved by appropriate fire protection agencies and insurance underwriters for use in storing such materials in "protected" warehouses (warehouses whose fire suppression systems and stacking patterns meet the requirements of Section 4.8 of NFPA-30, the Flammable and Combustible Liquids Fire Code).
Experience has shown that when composite IBCs are exposed to fire, the steel cage heats up, causing a transfer of heat from the steel cage to the plastic inner container. When this heat transfer exceeds the transfer of heat from the plastic inner container to the container's liquid contents, the temperature of the container increases. If the heat exposure from a fire is great enough, the temperature of the container along those areas where the steel cage contacts the container can increase to well above the melting point of the polyethylene, overwhelming the heat removal capability of the liquid contents, and causing failure of the container.
If failure of the inner container occurs, the flammable contents can spill out and be exposed to the fire, making it extremely difficult to extinguish the blaze. As a result of this heretofore unsolved problem, a significant market for steel cage reinforced IBCs has been foreclosed, or at least made difficult to serve.
The present invention solves this problem by coating the metal cage with an intumescent paint or other intumescent coating. When the intumescent coating is exposed to high temperatures, it swells and chars, producing a low density but coherent ash. The ash or char provides thermal insulation to the metal cage, preventing the temperature of the cage from increasing to the point where the cage will melt through the inner plastic container.
By maintaining the temperature of the inner container where it contacts the metal cage low enough so that the container does not quickly melt through, even in the presence of an intense warehouse fire, the present invention allows the survival of the composite IBC's plastic inner container for a time sufficient for alternative fire protection means (e.g., sprinklers, fire service personnel with water or foam spray fire suppression equipment) to be deployed.
While intumescent paints are known in the art, their use has been generally limited to building construction materials, double-walled storage tanks and the like. The present invention for the first time incorporates intumescent paint in the design of composite intermediate bulk containers as a means to protect composite IBCs from failure due to fire.
Thus it is an object of the present invention to markedly improve the fire resistance of IBCs having metal support structures.
A further object of the present invention is to provide a steel cage reinforced IBC wherein the steel cage is coated with an intumescent paint or coating such that, when the cage is exposed to fire, the paint or coating swells and chars, producing a low density but coherent ash.
A still further object of the present invention is to provide a self insulating metal support cage for an IBC which prevents the temperature of the cage from increasing to the point where the cage will melt through the inner plastic container.
Further and additional objects will appear from the description, accompanying drawing, and appended claims.